Conventionally, in an electric power station such as an electric substation or a switching station, puffer-type gas circuit breakers that extinguish an arc generated between electrodes by using blowing of insulation gas have been employed. Among these conventional circuit breakers, a mechanical-puffer-type gas circuit breaker extinguishes an arc by compressing insulation gas in a mechanical puffer chamber by a mechanical operation and blowing the compressed insulation gas to the arc. Further, a thermal-puffer-type gas circuit breaker extinguishes an arc by blowing insulation gas to the arc, which is compressed by heat of the arc. In addition, a mechanical-puffer/thermal-puffer hybrid-type gas circuit breaker that employs the mechanical type and the thermal type in combination has also been practically used.
A mechanical-puffer/thermal-puffer hybrid-type gas circuit breaker described in Patent Literature 1 includes a first thermal puffer chamber that is provided at an inner side of a movable contact, a second thermal puffer chamber that is fixed to a container, which is filled with insulation gas, and is always communicated with the first thermal puffer chamber, and a mechanical puffer chamber that is provided in series with the first thermal puffer chamber at an inner side of a movable contact and communicated with the first thermal puffer chamber via a check valve.
In the gas circuit breaker described in Patent Literature 1, when breaking a large current, pressures of the first and second thermal puffer chambers are increased by thermal expansion of the circumferential gas due to an energy of the arc generated between electrodes. When the pressures of the first and second thermal puffer chambers are increased higher than a pressure of the mechanical puffer chamber, a communicating port between the first thermal puffer chamber and the mechanical puffer chamber is closed by the check valve, and the compressed insulation gas in the first and second thermal puffer chambers is blown to the arc. When breaking a small current, the pressure of the mechanical puffer chamber is increased higher than the pressures of the first and second thermal puffer chambers by a mechanical compression, and thus the check valve between the first thermal puffer chamber and the mechanical puffer chamber is opened, and the compressed insulation gas in the mechanical puffer chamber is blown to the arc through the first thermal puffer chamber. In this method, an excessive puffer pressure when breaking a larger current can be transferred from the first thermal puffer chamber to the second thermal puffer chamber, and thus a puffer reaction force can be reduced. With this configuration, a required operation force of an operation device can be reduced.
In the conventional mechanical-puffer-type gas circuit breaker, even when the arc energy when breaking a small current is not large enough, a pressure increase can be obtained by reducing a volume inside the mechanical puffer chamber, and thus a sufficient puffer pressure can be obtained so that current breaking can be easily achieved.